A number of amorphous (including glass) and glass-ceramic compositions are known. Many oxide glass systems utilize well-known glass-formers such as SiO2, B2O3, P2O5, GeO2, TeO2, As2O3, and V2O5 to aid in the formation of the glass. Some of the glasses can be heat-treated to form glass ceramics.
Many properties of known glasses and glass-ceramics may be limited by the intrinsic properties of glass-formers. For example, for SiO2, B2O3, and P2O5-based glasses and glass-ceramics, the Young's modulus, hardness, and strength are typically limited by such glass formers. These glass and glass-ceramics generally have inferior mechanical properties as compared, for example, to Al2O3 or ZrO3.
In another aspect, in general, during most ceramic processing operations, it is desirable to obtain maximum densification with minimum grain size (e.g. without significant crystal growth). Exemplary ceramic processing techniques that may lead to minimizing grain size include decreasing crystal growth rate. Although not wanting to be bound by theory, in general, it is believed in the ceramic art that larger crystal sizes lead to reduced mechanical properties while finer average crystallite sizes lead to improved mechanical properties (e.g., higher strength and higher hardness).